Exhibit 99.1

FIRST FINANCIAL BANKSHARES ANNOUNCES

THIRD QUARTER EARNINGS RESULTS

ABILENE, Texas, October 19, 2017 – First Financial Bankshares, Inc. (NASDAQ: FFIN) today reported earnings for the third quarter of 2017 of $29.37 million, up 14.73 percent when compared with earnings of $25.60 million in the same quarter last year. Basic earnings per share were $0.44 for the third quarter of 2017 compared with $0.39 in the same quarter a year ago.

Net interest income for the third quarter of 2017 increased 5.22 percent to $59.69 million compared with $56.73 million in the same quarter of 2016. The net interest margin, on a taxable equivalent basis, was 3.94 percent for the third quarter of 2017 compared to 4.05 percent for the second quarter of 2017 and 4.04 percent for the third quarter of 2016. Included in interest income for the third quarter of 2017 was $450 thousand, or two basis points in net interest margin, related to discount accretion from fair value accounting related to the Conroe and Orange acquisitions.    

The provision for loan losses was $1.42 million in the third quarter of 2017 compared with $1.73 million in the second quarter of 2017 and $3.83 million in the third quarter of 2016. The continued provision for loan losses in 2017 reflects growth in the loan portfolio, the continued levels of gross charge-offs and the effects related to Hurricane Harvey. Nonperforming assets as a percentage of loans and foreclosed assets totaled 0.63 percent at September 30, 2017, compared with 0.71 percent at June 30, 2017, and 1.04 percent at September 30, 2016. Classified loans totaled $121.29 million at September 30, 2017, compared to $117.61 million at June 30, 2017, and $126.60 million at September 30, 2016. The higher provision for loan losses and nonperforming asset levels in the third quarter of 2016 when compared to the current period was primarily related to one nonaccrual commercial loan, which was in the process of liquidation at September 30, 2016, and has now been resolved.

At September 30, 2017, loans with oil and gas industry exposure totaled 1.99% of gross loans. These loans comprised $21.82 million of the classified loan totals and $1.57 million of the nonperforming loan totals. In addition, there were no net charge-offs related to these oil and gas loans for the quarter ended September 30, 2017. At September 30, 2017, the Company’s allowance for loan loss reserve specific to its total oil and gas loan portfolio totaled 6.03% of total oil and gas loans.

Noninterest income increased 9.52 percent in the third quarter of 2017 to $24.26 million compared with $22.15 million in the same quarter a year ago. Trust fees increased to $6.04 million in the third quarter of 2017 compared with $5.07 million in the same quarter last year, due to continued growth in the fair value of Trust assets managed to $4.92 billion from $4.22 billion a year ago. ATM, interchange and credit card fees increased 5.67 percent to $6.34 million compared with $6.00 million in the same quarter last year due to continued growth in debit cards. Service charges on deposits increased 5.98 percent to $5.08 million compared with $4.80 million in the same quarter a year ago due to continued growth in net new accounts. Also included in noninterest income during the third quarter of 2017 was a gain on sale of securities of $1.08 million compared to $239 thousand in the same quarter a year ago and an increase in other noninterest income of $629 thousand compared to the same quarter a year ago, primarily resulting from a $505 thousand litigation settlement. Offsetting these increases was a decrease in real estate mortgage fees of $806 thousand or 17.16% compared to the same quarter a year ago, partially due to the effects of Hurricane Harvey.

Noninterest expense for the third quarter of 2017 totaled $43.96 million compared to $42.00 million in the third quarter of 2016. The Company’s efficiency ratio in the third quarter of 2017 was 48.71 percent compared with 49.33 percent in the same quarter last year. The increase in noninterest expense in the third quarter of 2017 was primarily a result of an increase in salary and employee benefit costs to $24.14 million compared to $22.93 million in the same quarter a year ago, primarily due to merit based pay increases and profit sharing expenses. Additionally, operational and other losses increased $548 thousand when compared to the same quarter a year ago, primarily related to hurricane and fraud losses.

For the nine months ended September 30, 2017, net income increased 7.83 percent to $84.23 million from $78.11 million a year ago. Basic earnings per share rose to $1.27 from $1.18 in the same period last year. Net interest income increased 3.22 percent to $175.79 million for the nine months ended September 30, 2017, from $170.30 million in the same period a year ago. The provision for loan losses totaled $5.09 million compared with $8.22 million in the same period a year ago. Noninterest income was $68.72 million for the first nine months 2017 compared with $63.41 million in the same period a year ago. Noninterest expense rose to $129.89 million compared with $123.84 million during the same period a year ago.

As of September 30, 2017, consolidated assets for the Company totaled $7.01 billion compared to $6.95 billion at June 30, 2017, and $6.69 billion at September 30, 2016. Loans grew to $3.49 billion at September 30, 2017, compared with loans of $3.46 billion at June 30, 2017 and $3.37 billion at September 30, 2016. Deposits totaled $5.70 billion at September 30, 2017, compared to $5.63 billion at June 30, 2017, and $5.24 billion at September 30, 2016. Shareholders’ equity rose to $906.56 million as of September 30, 2017, compared with $887.44 million at June 30, 2017, and $867.94 million at September 30, 2016.

On October 12, 2017, the Company announced the pending acquisition of Commercial Bancshares, Inc. and its wholly owned subsidiary, Commercial State Bank headquartered in Kingwood, Texas. Commercial State Bank had total loans of $263.77 million, total deposits of $322.14 million and total assets of $366.83 at September 30, 2017.

“We continue to work diligently to grow loans and deposits, reduce expenses to improve our bottom line while continuing to look for acquisition opportunities like our recent Kingwood announcement to better utilize our strong capital position and increase returns to our shareholders,” said F. Scott Dueser, Chairman, President and CEO. “This quarter, many of our employees and customers in our Southeast Texas and Conroe regions were significantly affected by Hurricane Harvey. However, we are so proud of how swiftly our Company responded by getting our branches re-opened so we could meet the critical needs of our customers. With the help of our employees, directors and customers throughout our footprint, First Financial was able to raise over $300 thousand that was distributed to our employees that were most effected by the hurricane,” added Dueser.

The Company has regional locations surrounding Houston in the Conroe, Willis, Tomball, Huntsville, Montgomery and Magnolia markets and in Southeast Texas in Orange, Beaumont, Vidor, Newton, Mauriceville and Port Arthur. Several of these markets were impacted by Hurricane Harvey in late August. We continue to evaluate the effect of the hurricane on our branch facilities, loans and investment portfolio. To date, the amounts related to damages at our physical locations not covered by insurance do not appear to be significant. Combined, the Company had approximately $846.45 million in loans throughout these markets at September 30, 2017. We continue to evaluate these loans and the related collateral and business operations underlying these loans. We have provided additional allowance for loan

and lease losses as deemed appropriate based on our analysis. Our tax exempt municipal bonds in the counties of Texas effected by the hurricane have been evaluated, including insurance on the bonds. At September 30, 2017, our municipal bonds in these counties totaled $254.48 million. Based on analysis of these bonds and the related municipality, we do not believe we have any credit related other than temporary impairment.

About First Financial Bankshares

Headquartered in Abilene, Texas, First Financial Bankshares is a financial holding company that through its subsidiary, First Financial Bank, N.A., operates multiple banking regions with 69 locations in Texas including Abilene, Acton, Albany, Aledo, Alvarado, Beaumont, Boyd, Bridgeport, Brock, Burleson, Cisco, Cleburne, Clyde, Conroe, Cut and Shoot, Decatur, Eastland, Fort Worth, Glen Rose, Granbury, Grapevine, Hereford, Huntsville, Keller, Magnolia, Mauriceville, Merkel, Midlothian, Mineral Wells, Montgomery, Moran, New Waverly, Newton, Odessa, Orange, Port Arthur, Ranger, Rising Star, Roby, San Angelo, Southlake, Stephenville, Sweetwater, Tomball, Trent, Trophy Club, Vidor, Waxahachie, Weatherford, Willis, and Willow Park. The Company also operates First Financial Trust & Asset Management Company, N.A., with seven locations and First Technology Services, Inc., a technology operating company.

The Company is listed on The NASDAQ Global Select Market under the trading symbol FFIN. For more information about First Financial Bankshares, please visit our website at http://www.ffin.com

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Certain statements contained herein may be considered “forward-looking statements” as defined in the Private Securities Litigation Reform Act of 1995. These statements are based upon the belief of the Company’s management, as well as assumptions made beyond information currently available to the Company’s management, and may be, but not necessarily are, identified by such words as “expect”, “plan”, “anticipate”, “target”, “forecast” and “goal”. Because such “forward-looking statements” are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Factors that could cause actual results to differ materially from the Company’s expectations include competition from other financial institutions and financial holding companies; the effects of and changes in trade, monetary and fiscal policies and laws, including interest rate policies of the Federal Reserve Board; changes in the demand for loans; fluctuations in value of collateral and loan reserves; inflation, interest rate, market and monetary fluctuations; changes in consumer spending, borrowing and savings habits; and acquisitions and integration of acquired businesses, and similar variables. Other key risks are described in the Company’s reports filed with the Securities and Exchange Commission, which may be obtained under “Investor Relations-Documents/Filings” on the Company’s Web site or by writing or calling the Company at 325.627.7155. Except as otherwise stated in this news announcement, the Company does not undertake any obligation to update publicly or revise any forward-looking statements because of new information, future events or otherwise.

FIRST FINANCIAL BANKSHARES, INC.

CONSOLIDATED FINANCIAL SUMMARY (UNAUDITED)

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FIRST FINANCIAL BANKSHARES, INC.

SELECTED FINANCIAL DATA (UNAUDITED)

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FIRST FINANCIAL BANKSHARES, INC.

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